Ovary Development and Cold Tolerance of the Invasive Pest Drosophila suzukii (Matsumura) in the Central Plains of Kansas, United States.

Environmental challenges presented by temperature variation can be overcome through phenotypic plasticity in small invasive ectotherms. We tested the effect of thermal exposure to 21, 18, and 11°C throughout the whole life cycle of individuals, thermal exposure of adults reared at 25°C to 15 and 11°C for a 21-d period, and long (14:10 hr) and short (10:14 hr) photoperiod on ovary size and development in Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) cultured from a recently established population in Topeka, Kansas (United States). Examination of the response to temperature and photoperiod variation in this central plains population provides insight into the role of phenotypic plasticity in a climate that is warmer than regions in North America where D. suzukii was initially established. We found both low temperature and short photoperiod resulted in reduced ovary size and level of development. In particular, reduced ovary development was observed following exposure to 15°C, indicating that ovary development in females from the central plains population is more sensitive to lower temperature compared with populations examined from the northern United States and southern Canada. We also provide evidence that D. suzukii reared at 25°C are capable of short-term hardening when exposed to -6°C following 4°C acclimation, contrary to previous reports indicating flies reared at warm temperatures do not rapidly-cold harden. Our study highlights the central role of phenotypic plasticity in response to winter-like laboratory conditions and provides an important geographic comparison to previously published assessments of ovary development and short-term hardening survival response for D. suzukii collected in cooler climates.